Since you dropped it, the belt has been picked up by another player. Even if that were not the case, you would need to return to its location to retrieve it manually; it would not be assigned to you (nor would you need it assigned to you in order to pick it up, or remove the knife from the belt). It is strange, though, that one of the items still appears in your inventory while the other does not, but this should be automatically resolved once Kyle runs the full item script.